In flue gas, substances present in a solid form, such as dust, are generally mixed in with additional air pollutants present in a gaseous form, for example, NOx.
Known conventional removal means for fine solid particles in flue gas include cyclones making use of centrifugal force and bag filters relying upon filtration.
They are all employed to separate and collect only fine solid particles from flue gas. They cannot eliminate gaseous air pollutants so most of such air pollutants are released into the atmosphere.
To remove such gaseous air pollutants, a chemical facility is additionally required to use an aqueous solution which can absorb such air pollutants. In addition to a reaction tank in which the gaseous air pollutants react with the aqueous solution, this chemical facility is also equipped with an apparatus for recirculating the aqueous solution within the facility, an apparatus for feeding a fresh aqueous solution, an apparatus for treating the aqueous solution, etc.
To treat flue gas which contains a contaminant present in a solid form and an air pollutant in a gaseous form, a system constructed with a combination of a dust collector, such as a cyclone, and a chemical facility has heretofore generally been employed.
Such a conventional flue gas treatment system is, however, accompanied by the drawback that a very large chemical facility is required. Furthermore, the need to take into consideration corrosion resistance to the aqueous solution leads to a higher initial cost for the system, and the need for supply and treatment of the aqueous solution results in higher running cost.
In industrial fields where flue gas occurs in a huge volume during the course of manufacture of a product or the like, such as in the chemical and steel industries, there has hence been a strong desire for the development of a flue gas treatment system which can eliminate gaseous air pollutants without any chemical facility.
For industrial fields using an apparatus such as a small incinerator or boiler, such a flue gas treatment system is too large and too expensive. It is the current situation that, despite the immense concern about the pollution problem, no flue gas treatment system or apparatus is installed.